Geographic information systems provide for the archiving, retrieving, and manipulating of data that has been stored and indexed according to geographic coordinates of its elements. A geographic information system generally includes a variety of data types, including imagery, maps, three-dimensional models, tables, vector data (e.g. vector representations of roads, parcels, buildings, etc.) and other data. Improvements in computer processing power and broadband technology have led to the development of interactive geographic information systems that allow for the navigating and displaying of three-dimensional representations of geographic areas. For instance, a user of the geographic information system can control a virtual camera to navigate a three-dimensional representation of a geographic area of interest.
Textures, such as satellite images or aerial imagery, can be applied to a three-dimensional model of a geographic area to give the three-dimensional representation of the geographic area a more realistic appearance. When the textures for the three-dimensional representation are composited from a plurality of different source images, any illumination and exposure differences among the source images can lead to unnatural color discontinuities in the textured three-dimensional representation at the boundaries of the source images.
Source images of the geographic area can be blended to correct for discontinuities in the imagery provided in the geographic information system. Multi-band blending is a known technique for reducing color seams in mosaic images composited from a collection of source images that contain exposure or illumination differences. Applying a multi-band blending technique, however, may smooth out desirable color discontinuities that are due to real scene differences. For example, a bright roof of a building may be adjacent to a deeply shadowed wall and ground. If these surfaces are textured from two different source images, blending would attempt to even out the difference, leading to a smudged appearance in the imagery. For instance, the roof would become darker and the wall would become lighter. In addition, because multi-band blending primarily affects low spatial frequencies, the contrast of high frequency details remain low in the brightened areas, resulting in a washed-out appearance.